It is proposed to investigate the dynamic mechanical response of an in vivo long bone to mechanical impact and attempt to develop this into a clinical tool for quantitative measurement of the state of healing of a fracture in the bone. A mathematical model of the human and animal tibia will be developed which will predict the response of an accelerometer pressed against one end of the tibia due to a measured force on the opposite end. Animal experiments will be run in which the mechanical stiffness of a fracture in the live animal tibia will be predicted using the model and this compared with a direct measurement of the stiffness of the animal fracture. The model will then be used to predict the fracture stiffness of fractures in human tibias. If successful the technique will be put into clinical use.